Eclipse Jetty - Information Disclosure (CVE-2021-28169)
Description
For Eclipse Jetty versions <= 9.4.40, <= 10.0.2, <= 11.0.2, it is possible for requests to the ConcatServlet with a doubly encoded path to access protected resources within the WEB-INF directory. For example a request to /concat?/%2557EB-INF/web.xml can retrieve the web.xml file. This can reveal sensitive information regarding the implementation of a web application.
psychologyCrowdSec Analysis
CVE-2021-28169 is a vulnerability in Eclipse Jetty that allows remote attackers to access protected resources within the WEB-INF directory by exploiting doubly encoded paths in requests to the ConcatServlet. This flaw can expose sensitive files such as web.xml, potentially revealing critical information about the web application's internal configuration and implementation.
CrowdSec has been tracking this vulnerability and its exploits since 10th of September 2025.
Insights from the CrowdSec network reveal that the attackers trying to exploit CVE-2021-28169 are composed of a fairly even mix of opportunistic and targeted actors. Some attackers employ preliminary reconnaissance, while others use indiscriminate scanning. CrowdSec data also reveals a clear uptick in attacks involving CVE-2021-28169 over the past week. Activity is above the usual baseline, suggesting growing attention from attackers. This may reflect rising awareness, recent exploit releases, or expanded targeting efforts.
Attackers exploit this vulnerability by sending requests to endpoints such as /static or /concat with doubly encoded paths like /%2557EB-INF/web.xml to access sensitive files within the WEB-INF directory.
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| Event | Date |
|---|---|
| CVE Published | 2021-06-09 |
| Rule Released | 2025-09-10 |
| CrowdSec First Seen | 2025-09-12 |
Remediation & Protection
External References
- https://lists.apache.org/thread.html/rf36f1114e84a3379b20587063686148e2d5a39abc0b8a66ff2a9087a%40%3Cissues.zookeeper.apache.org%3E
- https://lists.apache.org/thread.html/rddbb4f8d5db23265bb63d14ef4b3723b438abc1589f877db11d35450%40%3Cissues.zookeeper.apache.org%3E
- https://github.com/eclipse/jetty.project/security/advisories/GHSA-gwcr-j4wh-j3cq
- https://lists.apache.org/thread.html/r234f6452297065636356f43654cdacef565b8f9ceb0e0c07ffb8c73b%40%3Cdev.kafka.apache.org%3E
- https://lists.apache.org/thread.html/ref1c161a1621504e673f9197b49e6efe5a33ce3f0e6d8f1f804fc695%40%3Cjira.kafka.apache.org%3E
- https://lists.apache.org/thread.html/rb1292d30462b9baedea7c5d9594fc75990d9aa0ec223b48054ca9c25%40%3Cjira.kafka.apache.org%3E
- https://lists.apache.org/thread.html/r91e34ff61aff8fd25a3f2a21539597c6ef7589a31c199b0a9546477c%40%3Cjira.kafka.apache.org%3E
- https://security.netapp.com/advisory/ntap-20210727-0009/
- https://lists.apache.org/thread.html/rfff6ff8ffb31e8a32619c79774def44b6ffbb037c128c5ad3eab7171%40%3Cissues.zookeeper.apache.org%3E
- https://lists.apache.org/thread.html/r04a4b4553a23aff26f42635a6ae388c3b162aab30a88d12e59d05168%40%3Cjira.kafka.apache.org%3E
- https://www.debian.org/security/2021/dsa-4949
- https://lists.debian.org/debian-lts-announce/2021/06/msg00017.html
- https://lists.apache.org/thread.html/r29678972c3f8164b151fd7a5802785d402e530c09870a82ffc7681a4%40%3Cdev.kafka.apache.org%3E
- https://lists.apache.org/thread.html/rd5b52362f5edf98e0dcab6541a381f571cccc05ad9188e793af688f3%40%3Cjira.kafka.apache.org%3E
- https://lists.apache.org/thread.html/r8a1a332899a1f92c8118b0895b144b27a78e3f25b9d58a34dd5eb084%40%3Cnotifications.zookeeper.apache.org%3E
- https://lists.apache.org/thread.html/r67c4f90658fde875521c949448c54c98517beecdc7f618f902c620ec%40%3Cissues.zookeeper.apache.org%3E
- https://lists.apache.org/thread.html/r32b0b640ad2be3b858f0af51c68a7d5c5a66a462c8bbb93699825cd3%40%3Cissues.zookeeper.apache.org%3E
- https://www.oracle.com/security-alerts/cpujan2022.html
- https://lists.apache.org/thread.html/r33eb06b05afbc7df28d31055cae0cb3fd36cab808c884bf6d680bea5%40%3Cdev.zookeeper.apache.org%3E
- https://www.oracle.com/security-alerts/cpuapr2022.html
- https://lists.apache.org/thread.html/r2721aba31a8562639c4b937150897e24f78f747cdbda8641c0f659fe%40%3Cusers.kafka.apache.org%3E
- https://www.oracle.com/security-alerts/cpuoct2021.html
- https://lists.apache.org/thread.html/rbefa055282d52d6b58d29a79fbb0be65ab0a38d25f00bd29eaf5e6fd%40%3Cnotifications.zookeeper.apache.org%3E
- https://lists.apache.org/thread.html/r284de9c5399486dfff12ab9e7323ca720dd7019a9a3e11c8510a7140%40%3Cjira.kafka.apache.org%3E
- https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2021/CVE-2021-28169.yaml